multi-faceted memory

schattenfiguren, 2014

i did not post a blog entry on march 22 since i was away on vacation. i was able to experience a wonderful journey through myanmar, cambodia and thailand, which included many human, cultural, geographical and of course photographical highlights.

my website will be available in english starting monday. i would like to welcome all interested english speakers.

multi-faceted memory

when looking at a photo, i can recognize people, a face, places or maybe situations. this requires a memory that allows me to acquire, memorize or retrieve information. that way i can remember experiences or plan my future according to my assessment of previous experiences. one could call that intelligent behavior (depending on the outcome).

the short-term memory memorizes and remembers instantaneously, but only with limited capacity. the long-term memory possesses a high store capacity with more stable memories. these are based on synaptic plasticity.

the long-term memory can again be divided into the declarative, explicit memory, where facts, but also automated actions are memorized (i.e. riding a bike, which is consciously learned at first and then turns into an automated process). this is consequently about relearning and unlearning.

the procedural, implicit memory is about “knowing how to”. emotional reactions (being afraid of an animal) and reflexes (closing your eyes in case of danger) are memorized here. the whole process follows the principle of pavlovian conditioning. this memorization aims at optimizing the chance of survival.

pavlov’s dog experiment works as follows: a bell sounds every time the dogs are fed, and the view of the delicious food naturally makes their mouths water. after some time the bell is rang without food being served – and this still makes the dogs’ mouths water. this means that the dogs show a conditioned reaction to the sound of the bell.

stimuli and information from our environment, but also from our bodies steadily enter our brain through our various senses. this could lead to excessive stimulus of our brain (an epileptic fit can be viewed as such an event). the brain keeps everything in order through the thalamus, the “gate” to the brain and the most important control center, which filters out irrelevant stimuli. that way many neurons remain unstimulated or are even debilitated. as long as i am strongly focusing on something, i am fading out irrelevant things like traffic noise, but i quickly react when someone calls my name.

a single neuron does not “know” anything. it is only groups of simultaneously activated neurons and their pattern formation that gain significance. in the learning process – and life is one big learning process – the involved neutrons group in specialized networks. as soon as one neuron has activated another neuron repeatedly, new contact points are created, which in addition become more sensitive and more stable (!), just as if the system would remember previous stimulation. this is called long-term potentiation (ltp).

the nervous system is very adjustable, adaptive and self organized!

the brain memorizes everything, some consciously, but most of it unconsciously. all our experiences, thoughts and imaginations, but also our actions and their consequences and not least our emotions (saved in the amygdala, part of the limbic system, deep inside the brain) determine our identity. just like we “rate” our past, it influences our view on the present and our actions in the future.

as a reminder: the memory as such does not exist. there are only different systems of processing and memorizing. memory therefore means that neuronal structures are being changed. this is called neuroplasticity of the brain.

sources: christof koch, manfred spitzer, gerhard roth, klaus grawe